The disarray in the U.S. space shuttle program after the Columbia disaster has left lawmakers wondering what the future of the country's manned space program should be. Experts tell Congress that the expensive shuttle fleet and international space station are limiting the possibilities for human space exploration.

On the day after China launched its first manned spacecraft, the House of Representatives Science Committee appealed to experts to provide a vision about where U.S. astronauts should go next in the solar system.

The problem, according to committee chairman Sherwood Boehlert, is that the 22-year-old space shuttle fleet and the fledgling international space station are not living up to their original promise.

"The space shuttle and the space station are remarkable achievements, but they are also extraordinarily expensive projects, and they haven't performed as advertised or done as much as hoped to advance human exploration or knowledge," he said. "We have to avoid going down the same paths in the future."

Nevertheless, shuttles and the station are the status quo for the U.S. space agency NASA, commitments made in the 1970s and '80s and now costing nearly half of its $15 billion annual budget. The agency is hoping to return the three remaining shuttles to flight in one year to continue building the station.

This huge outlay poses limits on the agency's flexibility because, as Science Committee members make clear, NASA's budget will not grow significantly in this era of deep national budget deficits. The former head of space science at NASA, Wes Huntress, says this leaves just two choices for U.S. manned space flight.

"One is, we have to give up our commitments to our foreign partners, we have to do something other than station and shuttle," he said. "Or the other path is that we continue business as usual because that's all that we can afford at the moment. That's unfortunate because it will have the tendency to perpetuate the current infrastructure."

But reneging on commitments to Washington's international space station partners is unappealing to a former chief of exploration at NASA, Michael Griffin. He says it would be difficult for the United States to lead if it fails to honor its promises.

"I would regret that because I believe there is value in the United States keeping its word," he said. "That said, if there is to be no more money available and if we are to undertake a program to do newer and better things, then there is no possibility other than closing off some of the old avenues and [redirecting] what we do."

But leaving this lesser-of-two evils scenario aside, most experts agree on the importance of getting humans beyond the low Earth orbit of the shuttle and space station and proceeding deeper into the solar system. Wes Huntress suggests that U.S. astronauts return to study the moon again and also head to Mars and near-Earth asteroids. This is a judgment reached by several independent expert panels since the mid-1980s and supported by geologist Bruce Murray, chairman of the Planetary Society.

"What we need is a destination that is worth risking human life and a lot of money, that is imaginative and uplifting, and Mars is clearly that," he said. "So, the president, if he really wanted to achieve a reversal of the decline we are in, would first have to say, 'I commit the United States of America in that direction.'

Mr. Murray recommends that human exploration of Mars be a joint international venture taken in incremental steps with incremental NASA budget increases to match.

To Michael Griffin, money should not be a worry because he says NASA is underfunded, costing the United States just 14 cents a day per person. He says just six cents a day per person more would buy a very robust human space flight effort.

"I spend more than that on chewing gum. We as a nation, quite literally, spend more on pizza than we do on space exploration. So I don't think we're overspending on space," he said.

Mr. Griffin asked Congress this question: Does it want a world in which human space flight programs of other nations are on the rise while that of the United States is in decline?